Cost-benefit analysis is a process by which business decisions are analyzed. It is used to estimate and total up the equivalent money value of the benefits and costs to the community of projects for establishing whether they are worthwhile. It is a term that refers both to:
helping to appraise, or assess, the case for a project, program, or policy proposal; an approach to making economic decisions of any kind. Under both definitions, the process involves, whether explicitly or implicitly, weighing the total expected costs against the total expected benefits of one or more actions in order to choose the best or most profitable option. The formal process is often referred to as either CBA (Cost-Benefit Analysis) or BCA (Benefit-Cost Analysis).
Answer option A is incorrect. Business Continuity Planning (BCP) is the creation and validation of a practiced logistical plan that defines how an organization will recover and restore partially or completely interrupted critical (urgent) functions within a predetermined time after a disaster or extended disruption. The logistical plan is called a Business Continuity Plan.
Answer option C is incorrect. Disaster recovery is the process, policies, and procedures related to preparing for recovery or continuation of technology infrastructure critical to an organization after a natural or human-induced disaster. Disaster recovery planning is a subset of a larger process known as business continuity planning and should include planning for resumption of applications, data, hardware, communications (such as networking) and other IT infrastructure. A business continuity plan (BCP) includes planning for non-IT related aspects such as key personnel, facilities, crisis communication and reputation protection, and should refer to the disaster recovery plan (DRP) for IT related infrastructure recovery / continuity.

Single key encryption uses a single word or phrase as the key. The same key is used by the sender to encrypt and the receiver to decrypt. Sender and receiver initially need to have a secure way of passing the key from one to the other. With TLS or SSL this would not be possible. Symmetric encryption is a type of encryption that uses a single key to encrypt and decrypt data. Symmetric encryption algorithms are faster than public key encryption. Therefore, it is commonly used when a message sender needs to encrypt a large amount of data. Data Encryption Standard (DES) uses the symmetric encryption key algorithm to encrypt data.

rootkit
Explanation:
A rootkit is a set of tools that take Administrative control of a computer system without
authorization by the computer owners and/or legitimate managers. A rootkit requires root access
to be installed in the Linux operating system, but once installed, the attacker can get root access
at any time. Rootkits have the following features:
They allow an attacker to run packet sniffers secretly to capture passwords.
They allow an attacker to set a Trojan into the operating system and thus open a backdoor for
anytime access.
They allow an attacker to replace utility programs that can be used to detect the attacker's activity.
They provide utilities for installing Trojans with the same attributes as legitimate programs.

Session hijacking refers to the exploitation of a valid computer session to gain unauthorized access to information or services in a computer system. In particular, it is used to refer to the theft of a magic cookie used to authenticate a user to a remote server. It has particular relevance to Web developers, as the HTTP cookies used to maintain a session on many Web sites can be easily stolen by an attacker using an intermediary computer or with access to the saved cookies on the victim's computer (see HTTP cookie theft).TCP session hijacking is when a hacker takes over a TCP session between two machines. Since most authentication only occurs at the start of a TCP session, this allows the hacker to gain access to a machine. Answer option A is incorrect. Spoofing is a technique that makes a transmission appear to have come from an authentic source by forging the IP address, email address, caller ID, etc. In IP spoofing, a hacker modifies packet headers by using someone else's IP address to hide his identity. However, spoofing cannot be used while surfing the Internet, chatting on-line, etc. because forging the source IP address causes the responses to be misdirected. Answer option B is incorrect. Smurf is an attack that generates significant computer network traffic on a victim network. This is a type of denial-of-service attack that floods a target system via spoofed broadcast ping messages. In such attacks, a perpetrator sends a large amount of ICMP echo request (ping) traffic to IP broadcast addresses, all of which have a spoofed source IP address of the intended victim. If the routing device delivering traffic to those broadcast addresses delivers the IP broadcast to all hosts, most hosts on that IP network will take the ICMP echo request and reply to it with an echo reply, which multiplies the traffic by the number of hosts responding. Answer option D is incorrect. Phishing is a type of scam that entices a user to disclose personal information such as social security number, bank account details, or credit card number. An example of phishing attack is a fraudulent e-mail that appears to come from a user's bank asking to change his online banking password. When the user clicks the link available on the e-mail, it directs him to a phishing site which replicates the original bank site. The phishing site lures the user to provide his personal information.